One of the most appalling and intellectually dishonest claims of Mitt Romney supporters is that President Obama is responsible for the increase in the national debt. The simple fact is that George W. Bush's tax cuts to the wealthy and his two wars were paid for with borrowed money. (Paul Ryan voted for these.)
These costs will continue to rise because Congress refuses to repeal the windfall given to their rich constituents, and refuses to raise war bonds to help defray that cost.
Another key factor in the rise of the nation's debt is the recession caused by the 2008 financial disaster that occurred before Obama took office.
The recession reduced tax revenues already depleted by Bush tax cuts. Obama added to the debt with temporary stimulus policies to help the wrecked economy. Republican governors then blamed their state workers for the economic woes and slashed state employees' jobs, increasing unemployment and further reducing the nation's tax base.
It is fair to say that Bush's policies will continue to add to the national debt until Congress does the right thing.